Oscillatory circuits



OSCILLATORY CIRCUIT Sv Filed March 20, 1-93'7 by` /YZWN/ lflvrlzeyPatented July 2, 1940 i UNITED sTATEs a PATENT foFEicE 2,206,238 yoscrLLAronY CIRCUITS Hans Rochow, Berlin-Lichterfelde, Germany, assignorto C. Lorena Aktiengesellschaft, Berlin- E Tempelhof, Lorenzweg,Germany, a company a Application March 20,

1937, Serial No. 132,050

In Germany April 4, 1936 p however, especially if arrangements for veryhigh l frequencies are concerned, difliculties arise `l through afrequency change which is independent ol the temperature of thesurrounding medium. This special frequency change may occur for in'-stance with discharge tubes of the kind having a glowing-cathode and oneor more additional .15 electrodes, being caused here by theinter-electrode capacities varying when the `tube is heated up. Suchcapacity variation will cause a frequency change of the oscillatorycircuits in which tubes of this kind `are included. 20 The invention hasfor its object to avoid these diflioulties and to such end provides forcompensating the said special frequency change in `a peculiar manner, aswill be understood from the following description and be particularly 25pointed out in the appended claim, reference being had to theaccompanying drawing that shows an example of a circuit arrangement asprovided by the invention.

The `example illustrated is a feed-back connec- 30 tion and comprises atube E that has three elec-` trodes one of which is a glowing-cathode C.

When heating up this tube the inter-electrode capacities, that is, thecapacities between cathode C, grid and anode, undergo` variation. In the35case of an indirectly `heated tube, for example,

this variation is such that after a certain time,

. for instance` 20 minutes, a definite value of the inter-electrodecapacities is reached.

In the example here disclosed the variation in the interelectrodecapacities is compensated by a variable additional capacity connected inparallel with the inter-electrode capacities and cone stituted by acondenser that consists of a metal plate A and a birnetallic strip orspring B. Plate A is connected to the anode, as shown. Spring` B isheated by a coil H connected in parallel with cathode C. Hereby thedistance between A and B and thus the additional capacity connected inparallel` with the inter-electrode capacities is so varied that avariation of these is compensated and that therefore a frequency changeof the oscillatory circuit pertaining to tube E will not occur. Spring Bis disposed in a jacket or any other casing or envelopment J made of amaterial which is a non-conductor of heat. By this means spring B isgiven a time constant which is equal to that of tube E, that is to say,the final capacity value of spring B is' reached in the same time asthat of tube E,

Whatis claimed is: l An oscillatory circuit including a glowing cathodetube and means associated therewith for opposing frequency changesresulting from changes in the constants of said tube during operationthereof comprising a condenser connected directly between the anode andcathode of said tube, a bi-rnetallic strip having an electrie heatingelement connected in parallel with `said cathode for varying thecapacity of said condenser and a heat insulating jacket surrounding'said strip and saidheating element, said jacket being so proportionedthat the final value of capacity of the said condenser as controlled bysaid loi-metallic strip is reached at the` same time as the fnalcapacityof said tube upon heating up of said circuit.

HANS ROCHOW.

